This invention relates to flexible conduit fixturing and, more particularly, to the substantial immobilization of flexible conduits such as are employed in thermocouples, fiber optic cables, heat transducers and the like.
Illustrative of the problem of fixturing is that of thermocouples. Now on the market are those constructed out of spiral wound stainless steel, flexible conduit onto which is screwed a threaded cap. The flexible conduit acts as a protective outer covering for the thermocouple element inside. It is used by inserting the flexible conduit into a hollow adapter and well or other well-providing means which has a 1/8" pin at a right angle to its top.
When the flexible conduit is pushed down and the cap is locked on the adapter or other receiving element, it acts as a spring to keep the thermocouple sensing tip at the end under tension. A serious problem arises in that the flexible conduit is free to turn inside the locking cap. In service, the thermocouple is locked onto the adapter which is often near or on the moving or reciprocating portion of a machine. The flexible conduit begins to work its way out of the cap causing the thermocouple tip (which is the sensing end) to lose tension with the surface completely. This leads to erroneous readings and worse, a runaway heating element.
One attempted solution to this problem is to provide a set screw in the cap but even this under heat, constant movement and the collapse of the thin stainless steel wall conduit under the set screw, eventually loosens.
The inventive fixturing solves this loosening problem in a different way. Instead of threading the cap as has been the past practice, a spring is fixed within the cap which fits inside the smaller loops of the stainless steel conduit. When the thermocouple is put into service by inserting it into the adapter and pushing down on the cap to capture it on the adapter pin, the spiral loops of the flexible conduit are compressed, closing on one another and capturing and locking the cap spring between them.
A search of the prior art relative to capequipped springs for thermocouples and like thin elements sheathed in flexible coupling revealed the following U.S. patents, none of which teach the concept of capturing a spring to immobilize the flexible conduit: U.S. Pat. Nos. 3,477,122, 3,522,107, 3,650,843, 3,679,490, 3,790,740, 3,751,305 and 3,930,891.